The mountain birch [Betula pubescens var. pumila (L.)] forest in the Subarctic is periodically exposed to insect outbreaks, which are expected to intensify due to climate change. To mitigate abiotic and biotic stresses, plants have evolved chemical defenses, including volatile organic compounds (VOCs) and non-volatile specialized compounds (NVSCs). Constitutive and induced production of these compounds, however, are poorly studied in Subarctic populations of mountain birch. Here, we assessed the joint effects of insect herbivory, elevation and season on foliar VOC emissions and NVSC contents of mountain birch. The VOCs were sampled in situ by an enclosure technique and analyzed by gas chromatography\uffe2\uff80\uff93mass spectrometry. NVSCs were analyzed by liquid chromatography\uffe2\uff80\uff93mass spectrometry using an untargeted approach. At low elevation, experimental herbivory by winter moth larvae (Operophtera brumata) increased emissions of monoterpenes and homoterpenes over the 3-week feeding period, and sesquiterpenes and green leaf volatiles at the end of the feeding period. At high elevation, however, herbivory augmented only homoterpene emissions. The more pronounced herbivory effects at low elevation were likely due to higher herbivory intensity. Of the individual compounds, linalool, ocimene, 4,8-dimethylnona-1,3,7-triene, 2-methyl butanenitrile and benzyl nitrile were among the most responsive compounds in herbivory treatments. Herbivory also altered foliar NVSC profiles at both low and high elevations, with the most responsive compounds likely belonging to fatty acyl glycosides and terpene glycosides. Additionally, VOC emissions from non-infested branches were higher at high than low elevation, particularly during the early season, which was mainly driven by phenological differences. The VOC emissions varied substantially over the season, largely reflecting the seasonal variations in temperature and light levels. Our results suggest that if insect herbivory pressure continues to rise in the mountain birch forest with ongoing climate change, it will significantly increase VOC emissions with important consequences for local trophic interactions and climate.
", "keywords": ["0301 basic medicine", "Volatile Organic Compounds", "0303 health sciences", "secondary metabolites", "VDP::Zoologiske og botaniske fag: 480", "plant\u2013insect interactions", "Moths", "15. Life on land", "geometrid moth", "Plant Leaves", "03 medical and health sciences", "biotic stress", "13. Climate action", "volatile organic compounds", "Larva", "8. Economic growth", "11. Sustainability", "VDP::Zoology and botany: 480", "Animals", "Herbivory", "Seasons", "global change", "Betula", "Research Paper"]}, "links": [{"href": "http://academic.oup.com/treephys/article-pdf/41/6/1019/38497290/tpab023.pdf"}, {"href": "https://doi.org/10.1093/treephys/tpab023"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Tree%20Physiology", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1093/treephys/tpab023", "name": "item", "description": "10.1093/treephys/tpab023", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1093/treephys/tpab023"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2021-02-18T00:00:00Z"}}, {"id": "10.1111/een.12679", "type": "Feature", "geometry": null, "properties": {"updated": "2026-07-25T16:18:40Z", "type": "Journal Article", "created": "2018-10-05", "title": "Ecological stoichiometry and nutrient partitioning in two insect herbivores responsible for large\u2010scale forest disturbance in the Fennoscandian subarctic", "description": "1. Outbreaks of herbivorous insects can have large impacts on regional soil carbon (C) storage and nutrient cycling. In northernmost Europe, population outbreaks of several geometrid moth species regularly cause large\uffe2\uff80\uff90scale defoliation in subarctic birch forests. An improved understanding is required of how leaf C and nutrients are processed after ingestion by herbivores and what this means for the quantity and quality of different materials produced (frass, bodies).
2. In this study, larvae of two geometrid species responsible for major outbreaks (Epirrita autumnata and Operophtera brumata) were raised on exclusive diets of Betula pubescens var. czerepanovii (N. I. Orlova) H\uffc3\uffa4met Ahti and two other abundant understorey species (Betula nana, Vaccinium myrtillus). The quantities of C, nitrogen (N) and phosphorus (P) ingested and allocated to frass, bodies and (in the case of C) respired were recorded.
3. Overall, 23%, 70% and 48% of ingested C, N and P were allocated to bodies, respectively, rather than frass and (in the case of C) respiration. Operophtera brumata consistently maintained more constant body stoichiometric ratios of C, N and P than did E. autumnata, across the wide variation in physico\uffe2\uff80\uff90chemical properties of plant diet supplied.
4. These observed differences and similarities on C and nutrient processing may improve researchers' ability to predict the amount and stoichiometry of frass and bodies generated after geometrid outbreaks. 1. Outbreaks of herbivorous insects can have large impacts on regional soil carbon (C) storage and nutrient cycling. In northernmost Europe, population outbreaks of several geometrid moth species regularly cause large\uffe2\uff80\uff90scale defoliation in subarctic birch forests. An improved understanding is required of how leaf C and nutrients are processed after ingestion by herbivores and what this means for the quantity and quality of different materials produced (frass, bodies).
2. In this study, larvae of two geometrid species responsible for major outbreaks ( Epirrita autumnata and Operophtera brumata ) were raised on exclusive diets of Betula pubescens var. czerepanovii (N. I. Orlova) H\uffc3\uffa4met Ahti and two other abundant understorey species ( Betula nana , Vaccinium myrtillus ). The quantities of C, nitrogen (N) and phosphorus (P) ingested and allocated to frass, bodies and (in the case of C) respired were recorded.
3. Overall, 23%, 70% and 48% of ingested C, N and P were allocated to bodies, respectively, rather than frass and (in the case of C) respiration. Operophtera brumata consistently maintained more constant body stoichiometric ratios of C, N and P than did E. autumnata , across the wide variation in physico\uffe2\uff80\uff90chemical properties of plant diet supplied.
4. These observed differences and similarities on C and nutrient processing may improve researchers' ability to predict the amount and stoichiometry of frass and bodies generated after geometrid outbreaks.